How do you step back and wait for the catastrophe?

My parents live in a four story home. Actually they live in the chilly, dark dungeon of a basement in a four story home because my father cannot walk up stairs. There are stairs between the basement and garage and the bathroom shower has a curb. He has PD, extremely poor balance, and cannot walk unassisted. He refuses to use a walker, rollator or wheelchair. They have had doctors, therapists, social workers, friends and family tell them that the home is a death trap, but they will not move. My mother thinks he will get better and my father just goes along with it. My mother who has hoarding tendencies has filled the upper stories with piles of papers and doodads and junk she still buys by the carload. He has had many falls, bruises, cuts, broken ribs, and black eyes but acts like it was nothing and my mother refuses to acknowledge that he has fallen more than once or twice. Always she has some ridiculous excuse to explain it away. They should be in independent or assisted living, but insist they are too healthy. I tried taking them house hunting for a more suitable home, with a first-floor master bed, kitchen and garage, but after weeks of that realized they were just humoring me and have no intention of moving. I just have to wait for something so awful to happen that they are forced to move, like to the hospital and then to a nursing home. It is hard to accept there is nothing I can do. When I talk to relatives I feel like it is my fault that they will not move. How do I find peace with their decision to live this way? It is like my parents want the whole family to watch while they are tied to a train track with the train just around the corner, whistling.